1. Field of the Invention
The present invention relates to a chassis having reduced acoustic noise and electromagnetic emissions, and to a method of cooling components within a chassis.
2. Background Art
Conventional electrical and electronic components generate considerable heat energy during operation. Such components are frequently housed in a chassis, which restricts the amount of ambient cooling air flow available to cool the components, resulting in high temperatures within the chassis. This condition is undesirable because high temperatures negatively affect the performance of electrical and electronic components, and can damage or shorten the life of a component if the temperature of the component becomes too high.
The heat generation problem has grown in significance because of the increased power requirements, and therefore increased heat generation, of modern electrical and electronic components. For example, the processing power of computers has increased dramatically in recent years, which has resulted in higher heat generation from components mounted on computer motherboards.
One conventional solution to the problem of heat generation is the use of cooling fans within a chassis to cool components within the chassis. While fans are effective for cooling electrical and electronic components, they generate acoustic noise during operation, which is undesirable. Acoustic noise is distracting to an operator, and the acoustic noise emanating from a large number of chassis negatively affects worker efficiency. Further, as components become more powerful, and generate more heat, larger and more powerful fans are required to cool the components within a chassis, which generates even more acoustic noise. Therefore, there is a practical limit to the amount that chassis cooling capacity can be increased by using larger, more powerful fans.
In addition to the large heat generation by modern electrical and electronic components, components also generate electromagnetic radiation during operation. Electromagnetic radiation is undesirable because it may interfere with radio, television, telephone, etc. transmissions, and many electronic devices are therefore subject to regulation by the Federal Communications Commission (FCC). FCC regulations restrict the amount of various types of radiation that a chassis can emit into the surrounding environment.
Conventional techniques for restricting the amount of electromagnetic radiation emitted by a chassis render it more difficult to cool components within the chassis, and ultimately result in a chassis that generates more acoustic noise. For example, one conventional solution is to place grilles over a chassis"" air intake port and air exhaust port, the grilles being designed to restrict the escape of electromagnetic radiation out of the chassis. A conventional grille includes several small holes for admitting cooling air into and out of the chassis, the diameter of the holes being chosen to prevent the escape of electromagnetic radiation from the chassis. While a small hole diameter for the grilles controls the escape of electromagnetic radiation from the chassis, it negatively affects the chassis"" cooling capacity. This occurs because the small holes in the grilles impair the flow of cooling air into and out of the chassis, and therefore larger, faster, more powerful fans must be employed in order to draw air through the chassis for cooling. The larger fans generate more acoustic noise, which is undesirable.
Therefore, a need exists for a chassis and a method of cooling a chassis that provide sufficient cooling for electrical or electronic components in the chassis, without generating excessive acoustic noise during operation. A need also exists for a chassis and a method of cooling a chassis that provide sufficient cooling for electrical or electronic components, without allowing excessive electromagnetic radiation to escape from the chassis.
The present invention satisfies the above needs and achieves other advantages not present in conventional devices. According to a first aspect of the present invention, a chassis for housing components comprises a shell having an intake port, and intake duct in fluid communication with the intake port, an exhaust port, an exhaust duct in fluid communication with the intake duct and in fluid communication with the exhaust port, and at least one air moving device. At least one of the intake duct and the exhaust duct include a noise attenuating feature, the noise attenuating feature attenuating acoustic noise generated within the chassis.
According to the first aspect of the invention, acoustic noise generated within the chassis is reduced by the noise attenuating feature before the acoustic noise escapes the chassis. The chassis thus operates more quietly.
According to a second aspect of the present invention, a plenum may be provided within the chassis to distribute cooling air within the chassis. The plenum includes apertures oriented near preselected components or zones within the chassis, so that cooling air is directed onto the preselected components or zones.
According to the second aspect of the invention, cooling air is efficiently distributed in the chassis, which reduces the power requirements for the air moving device and/or reduces the number of air moving devices required to cool the chassis. The use of fewer and/or less powerful air moving devices reduces acoustic noise generated within the chassis.
According to a third aspect of the present invention, a chassis comprises a shell, an intake port in the shell, an intake duct in fluid communication with and disposed to receive a flow of cooling air from the intake port, an exhaust port in the shell in fluid communication with the intake duct, an exhaust duct disposed in fluid communication with the intake port and the exhaust port, and at least one air moving device in fluid communication with the intake and exhaust ports. At least one of the intake duct and the exhaust duct has a cross sectional area and a length selected so as to attenuate selected frequencies of electromagnetic radiation generated within the chassis.
According to the third aspect of the invention, electromagnetic radiation is attenuated in either the intake duct or the exhaust duct, and grilles with very small apertures need not be placed over the intake and exhaust ports to attenuate electromagnetic radiation. Therefore, cooling air flow is not restricted by the small apertures, and less powerful, quieter fans can be used to cool the chassis.